Talc beneficiation



United States Patent 3,459,299 Patented Aug. 5, 1969 3,459,299 TALC BENEFICIATION Venaneio Mercade, Metuchen, N.J., assignor, by mesne assignments, to Engelhard Minerals & Chemicals Corporation, Menlo Park, Edison, N.J., a corporation of Delaware No Drawing. Filed Sept. 1, 1967, Ser. No. 664,934 lnt. Cl. 1803b 1/00; B03d N02 US. Cl. 209-3 12 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Talc is a magnesium silicate mineral which has natural floatability. This property has been used in the past to separate talc from gangue minerals such as tremolite and alkaline earth carbonates such as magnesite. In floating platy talc from magnesiite gangue on a commercial basis it has been the practice to carry out the flotation in the presence of frothers, such as pine oil and emulsified kerosene and, more recently, sodium alkylarylsulfonates. A description of a commercial talc beneficiation operation (Eastern Magnesia T alc Company) utilizing froth flotation to concentrate talc from magnesite in a Vermont talc Ore appears in Taggarts Handbook of Mineral Dressing, 3-122 (1945). Amines have also been used to float talc, especially fibrous tale.

The following patents deal with the flotation of talc: US. 2,337,118 to John Frank Lontz, which describes the use of the combination of a cationic surface active agent and a carboxylic acid amide to float siliceous minerals such as talc from carbonate minerals; US. 3,102,856 to Walter Eugen Chase, which describes the selective flotation of platy talc from nonplaty talc in a very dilute pulp at a pH of 6.8 to 8.0 in the presence of a frother, especially polypropylene glycolmethyl ether or the like, and a surface active agent, preferably an anionic alkyl sulfo succinate; US. 3,102,855 to Whitman E. Brown et al., which describes a process similar to that described in US. 3,102,856 except that a surface active agent is not used; US. 2,442,455 to Robert B. Booth et al., which discloses the flotation of tale in the presence of a water-soluble petroleum sulfonate of the green-acid type and oil; US. 2,748,935 to Rescheneder deals with the separation of talc from asbestos by a process which utilizes a surface active material without flotation.

THE INVENTION An object of the invention is the provision of an improved method for floating talc from alkaline earth carbonate gangue.

I have discovered that the flotation of talc from alkaline earth carbonate gangue is enhanced when the flotation is carried out in the presence of small amounts of an alkaline dispersing (deflocculating) agent such as sodium silicate or a sodium condensed phosphate and a specific type of nonionic surface active agent, namely, a water-dispersible nonionic fatty acid alkanolamide formed by condensing a higher unsaturated fatty acid material, such as soybean fatty acids, with diethanolamine. The nonionic surface active agent can be employed alone or in combination with a small amount of an auxiliary frother, such as an anionic sodium alkylarylsulfonate.

An essential feature of the invention resides in the use of an alkanol'amide flotation reagent containing an aliphatically unsaturated group derived from a high fatty acid. The desired results are not realized with nonionic saturated fatty acid alkanolamides such as coconut fatty acid diethanolamide or lauric acid diethanolamide.

Another essential feature of the flotation process is that the ore pulp is deflocculated with an alkaline dispersing agent during the flotation and the flotation is carried out in an alkaline pulp.

The fatty acid alkanolamides that are used in carrying out this invention function as froth controlling agents and flotation promotors, producing higher grade talc concentrates when used alone or with alkylarylsulfonates than are obtained with the prior art alkylarylsulfonates when employed alone. Froth concentrates obtained with the alkanolamide alone or in combination with alkylarylsulfonate have a higher content of acid insolubles (indicating less carbonate impurity) than concentrates obtained using the alkylarylsulfonates of the prior art as the sole frother. Using the alkanolamides alone or in combination with alkylarylsulfonates, the tale concentrates are also brighter in appearance, further indicating the higher purity of the concentrates. When the concentrates are micronized to place them in a condition required for some pigment purposes, the products obtained by flotation in the presence of alkanolamides are significantly brighter than products obtained with the alkylarylsulfonates alone. For example, a 90.1% brightness micronized talc concentrate analyzing 97.30% acid insolubles was obtained by floating unfractionated Vermont talc ore in the presence of soybean fatty acid diethanolamide. When the same amount of sodium dodecylbenzene sulfonate was used, the brightness of the milled talc was only 86.2% and acid insoluble content was only 94.59%.

Talc recovery is high in carrying out the process of the invention. Therefore, the process lends itself to the flotation of whole (unfractionated) ore, although the invention is not limited thereto. The benefit of applying flotation to a whole ore from Vermont (supra) is illustrated by the fact that I was able to recover more than twice as much tale in the form of products meeting the Federal Specifications of a minimum of 78% acid insolubles than was obtained in the commercial operation in which a fine cut from a tabling operation was floated. In fact, more than twice as much talc containing 88% or more acid insolubles was obtained by carrying out my process. 0f the 88% plus grade talc, a substantial portion was in the form of an exceptionally high grade talc concentrate (96% plus acid insolubles) which was not obtained in any of the fractions of the commercial operation.

The fatty acid alkanolamides (alkylolamides) employed in carrying out this invention are obtained by condensing a higher unsaturated fatty acid containing 14 to 22 carbon atoms or a mixture of fatty acids containing a substantial quantity of such aliphatically unsaturated fatty acids with diethanolamine in a 1:1 ratio. C-18 unsaturated acids are especially preferred. The resulting unsaturated fatty acid alkylolamides may be represented by the structure:

CHgCHlOH wherein R is an alkenyl group containing 15 to 21 carbon atoms.

The preparation of fatty acid alkanolamides, including those of the type employed in carrying out the present in- 3 vention, is described in US. 2,094,609 to Wolf Kritchevsky; US. 2,173,909, also to Kritchevsky deals with the use of fatty acid alkanolamides in ore flotation.

Unsaturated higher fatty acids that may be employed to produce the unsaturated fatty acid diethanolamides in clude myristoleic, palmitoleic, oleic, elaidic, lrnolelc, eleostearic, linolenic and erucic acid, as well as hydroxysubstituted acids such as ricinoleic. Fatty acids derived from naturally occurring glycerides such as corn oil fatty acids, cottonseed fatty acids, linseed fatty acids and soybean fatty acids are especially useful as the source of the fatty acid component. Glyceride esters of higher fatty acids such as animal fatty acids are suitable. Generally speaking, the source of the fatty acid component should contain at least 50% by weight of unsaturated acids. Such fatty acids have a Wijs iodine value of at least 100 (g. I /l g. sample).

Soybean fatty acid diethanolamide is the presentl preferred reagent because of its availability. Representative samples of soybean acids contain about 51% linoleic and 8.5% linolenic acid and contain a total of about 85% by weight unsaturated fatty acid, principally C-l8 unsaturated fatty acid. The compositions of suitable naturally occurring fats and oils are reported in Encyclopedia of Polymer Science and Technology, volume I, pages 100- 101, published by Interscience Publishers (1964).

In putting my invention into practice, the ore may be coarsely ground by conventional means, such as a jaw crusher, and milled to a size (e.g., minus 200 mesh) sufiicient to liberate the mineral values. When using whole ore it is preferable to wet-mill the crushed ore in order to prevent smearing of the gangue by talc which would reduce talc recovery.

Preferably, the ore is wet-milled in the presence of a dispersant such as a water-soluble grade of sodium silicate or a sodium condensed phosphate salt such as tetrasodium pyrophosphate or sodium hexametaphosphate. Mixtures of sodium silicate and sodium condensed phosphates may be employed. From 1 to l0#/ton of dispersant is used. Excellent results were obtained with a tale ore which was wet-ground in the presence of sodium silicate to 100% by weight finer than 200 mesh (equivalent spherical diameter). The resulting concentrate contained 50% by weight of particles finer than 22 microns. (The particle measurements were made by standard sedimentation method using 2.75 g./ml. as a density value in computing particle size from sedimentation rate data.)

As an alternative to the addition of the dispersant in the grinding circuit, the dispersant may be added to a pulp of the ground ore. In this case, the pulp should be thoroughly agitated (conditioned) with the dispersant.

It is also within the scope of this invention to incorporate a small amount (e.g., from 0.1 to 1 lb./ton) of a water-soluble polyvalent metal salt, preferably an aluminum salt, into the pulp before the pulp is conditioned with a frother. The salt may be incorporated into a dilute solution of sodium silicate dispersant to form a stable hydrosol before the pulp is dispersed with the sodium silicate. Reference is made to my copending application, Ser. No. 415,503, filed Dec. 2, 1964, now US. 3,337,048, for a detailed description of the preparation of the hydrosols.

As mentioned, the process is not limited to the flotation of whole ore. By way of example, it is within the scope of the invention to float talc from carbonate materials such as magnesite or dolomite and accessory minerals in an ore fraction obtained by crushing the whole ore, fine milling and air classifying to obtain a fine cut that is useful without further treatment and a coarse cut which is floated in a dispersed alkaline pulp in the presence of alkanolamide, in accordance with the present invention.

With some ores it may be desirable to deslime the dispersed pulp before conditioning with the flotation reagents.

The use of fairly dilute pulps, e.g., pulps containing 10% to 20% solids, is recommended for the conditioning step. Since wet-grinding is normally carried out at higher solids, wet-ground pulps should be diluted to an appropri ate solids content for conditioning.

In a presently preferred form of the invention, the pulp is initially conditioned with 0.1 to 0.5#/ton of a watersoluble sodium alkylarylsulfonate frother such as sodium dodecylbenzene sulfonate. If this pulp were aerated, a voluminous persistent froth would result. The alkanolamide froth promotor is then added in amount within the range of 0.1 to 0.5 #/ton of ore and the pulp is conditioned. The specific type of alkanolamide that is used results in a compact, brittle froth when used alone or in combination with the alkylarylsulfonate. The conditioned pulp has a pH within the range of about 9 to 11.

The pulp is aerated and a rough concentrate withdrawn. The rougher tailings may be discarded. The rougher concentrate may be floated again, without addition of reagents, producing a very high grade talc concentrate and a cleaner tailing product which, in many cases, is useable for some commercial applications of talc products.

While alkylarylsulfonates are the preferred secondary frothers, other frothers such as pine oil may be employed with the unsaturated fatty acid alkanolamide.

The iron minerals are depressed by the dispersants that are employed in carrying out the process of the invention. Tests indicate that the iron remaining with the tale after flotation is present in the lattice of the talc crystals.

The froths are processed by thickening, filtration, washing and drying. Talc products adapted for pigments may be micronized by means such as vertical hammer mills or fluid energy grinding equipment to produce pigments of desired particle size, e.g., minus 5 to 6 microns or finer.

EXAMPLES The tale used in the examples which follow was crushed run-of-mine ore from a deposit in the northern part of Vermont. The ore analyzed 64.76% acid soluble, 5.81% Fe O 0.70% A1 0 0.28% S, 13.94% CO 32.06% (MgO+CaO) and 3.62% H O. Based upon microscopic inspection, an X-ray diffraction pattern, chemical analysis and previous mineralogical studies of this type of ore, the mineral composition can be summarized as being a mixture of talc (largely fibrous with some platy talc) and magnesite accompanied by minor amounts of pyrite, pyrrhotite, gersdorffite, chlorite, actinolite, ankerite and iron oxides (some of which are magnetic).

Representative samples of the whole talc ore had an acid insoluble content of 63% to 65%. The ore was supplied as lumps approximately /8" and was crushed to minus 8 mesh (Tyler).

At present this ore is ground, tabled and a fine size fraction of the tabled ore floated, producing float products analyzing 88% to 92% acid insolubles and having brightness values (after fluid energy grinding) of 86% to 89%. In the process, the yield of commercial talc products is 36.7%, of which only about half represents the yield high purity floated grades.

The objective of the tests was to apply flotation to the run-of-mine ore and obtain a high yield of high brightness, high purity talc.

1 Reagents used in the examples are identified as folows:

Sodium silicate solution contains 9.16% Na O, 29.5%

SiO and the balance substantially water.

'Ultrawet DSA water-soluble anionic surface active agent-principally dodecylbenzene sodium sulfonate. Monamid -ADYA water-dispersible, oil-soluble nonionic surface active agentthe condensation prodnet of soybean fatty acids with diethanolamine in a 1:1

ratio; reported to contain 88% amide.

Example I Tests were carried out to demonstrate the advantages offioatmg the Vermont talc ore in the presence of a fatty acid alkanolamide reagent.

1. FLOTATION WITH ALKANOLAMIDEi ALONE A 500 gram sample of the minus 8 mesh talc was ground in a pebble mill with 470 ml. deionized water and 30 ml. of a 5% equeous solution of brand sodium silicate, corresponding to the use of 6.0 lbs./ ton of the 0 brand sodium silicate per ton of talc. The charge was ground for 30 minutes in the pebble mill and the minus 200 mesh pulp that was formed was transferred to a 500 g. capacity Airflow flotation machine and diluted to 12.5% solids with deionized water. Monamid ISO-ADY was added as a 1% aqueous dispersion in amount to provide 0.5 lb./ton of the alkanolamide and the pulp was conditioned for minutes. The pH of the conditioned pulp was 10.0. A rougher float was removed after 12 minutes. This float product was cleaned twice by froth flotation without addition of reagents.

Following are the metallurgical results:

TABLE I.-METALLURGICAL RESULTS-FLO'IATION OF TALC WITH SOYBEAN FATTY ACID ALKANOLAMIDE Acid Talc F6203 insoldistridistriubles, bution, FezOa, button, Wt. wt. wt. wt. wt. percent percent percent 1 percent percent Rougher tails 48. 6 43. 66 33. 1 8. 31 64. 3 Cleaner tails 1-2 19. 9 64. 31 20. 3 5. 89 18. 7 Talc concentrate 31. 5 93. 57 46. 6 3. 39 17. 0 Heads 100. 0 2 63. 23 100. 0 2 6. 28 100. 0

1 Estimated from acid-insoluble data. 1 Calculated value.

3. FLOTATION WITH SODIUM ALKYLARYLSULFONATE ALONE Test No. 1 was repeated using 0.25 lb./ton Ultrawet DS instead of the Monamid reagent.

Flotation products of the three tests were analyzed chemically and metallurgical results were evaluated in order to ascertain the effect of the use of the alkanolamide reagent on the floated talc product. Talc concentrates were analyzed for acid insolubles. The brightness of concentrates was also measured with a GE. Recording Spectrophotometer color analyzer which is described by Hardy, A. C., Journal Optical Soc. A., 2'8, (1938). Samples of the talc concentrates were fluid energy ground with compressed air as the fluid and brightness measurements of the micronized products obtained. The fluid energy mill was operated under conditions which reduced the minus 20 micron concentrate to minus 7 microns (average particle size about 2.3 microns).

The results of the three tests are summarized in Table II.

TABLE II.EFFECT OF ALKANOLAMIDE having 90.1% brightness (after grinding) and 96.32% to 97.30% acid insolubles were obtained. A product having a milled brightness of only 86.2% and a grade of 94.59% was produced when flotation was carried out in the absence of an alkanolamide. These results therefore show that brighter, more pure talc products were obtained by using the alkanolamide alone or together with the alkylarylsulfonate frother. This indicates that the alkanolamide was more selective to the flotation of talc than the sulfonate was.

Data in Table II show also that 37.07% of the tale was recovered by the single rougher flotation and two cleaner flotations when the alkanolamide was used in combination with the sulfonate. The recovery was 38.5% when the alkylarylsulfonate was used alone and 31.5% when the alkanolamide was used alone. These results indicate that it is preferable to use the alkanolamide along with a frother of the alkylarylsulfonate type in order to obtain higher recoveries of beneficiated talc than may be obtained with the alkanolamide alone.

Iron analyses showed that talc products contained less iron (3.34% and 3.39% Fe O when alkanolamide was used alone or with the sulfonate than when the sulfonate was used alone (3.58% Fe O This also indicates that the Monamid was more selective to talc.

Example II In Example I, the Ultrawet DS reagent had been used in amount of 0.25 lb./ton in the tests in which it was used as the sole frother and when used with 0.25 lb./ton Monamid. The Monamid had been employed in amount of 0.50 lb./ton when used as the sole surface active material. In order to show that the benefits, demonstrated in Example I, were not realized merely as the result of the use of a larger total quantity of frother, a test similar to Test N0. 3 was carried out using 0.50 lb./ ton Ultrawet DS as the sole frother.

In this test, talc recovery was only 30.8%, much less than the recovery obtained with 0.25 lb./t-on Ultrawet .DS alone or in combination with 0.25 lb./ ton Monamid -ADY. Moreover, the brightness of the ground beneflciated talc was only 81.6% and grade was 89.70%, indicating that the product was much less pure than any of the products obtained in Example I.

Example III In the previous examples the ground talc ore was dispersed with sodium silicate before flotation. To demonstrate the effectiveness of a sodium condensed phosphate dispersant, Test No. 2 of Example I was repeated using 0.2 lb./ton tetrasodium phosphate (Na P O in lieu of 0.6 lb./ton 0 brand sodium silicate. As in Test No. 2, the flotation reagents were 0.25 lb./ton Ultrawet DS and 0.25 lb./ ton Monamid 150-ADY.

The results were generally similar to those realized in Test No. 2 with the exception that talc recovery was only 33.3%, as compared to 37.0% when using sodium silicate to disperse the pulp. The product had a grade of ON THE FLO'IATION OF VERMONT TALC ORE Reagents, quantity in lbs/ton Talc concentrates Brightness "0 Brand Monamid Acid insolublcs, After fluid Test No NazSiOa Ultrawet DS 150-ADY percent Wt. percent As is energy grinding 1 6. 0 I None 0. 50 97. 30 31. 5 81. 7 90. 1 6. 0 0. 25 0. 25 96. 32 37. O 81. 9 90. 1 6. 0 0. 25 None 94. 59 38. 5 80. 8 86. 2 v

Fhe results in Table II show that by using the unsaturated fatty acid alkanolamide alone or in combination with the sodium alkylarylsulfonate, talc concentrates 97.58% and brightness before grinding of 83.1%. After grinding brightness was 89.8%

The results therefore indicate that a sodium condensed phosphate is an effective dispersant in the flotation beneficiation of talc ore with an unsaturated fatty acid alkanolamide flotation reagent.

Example IV Test No. 2 of Example I (6.0 lbs/ton ,O brand sodium silicate and 0.25 lb./ton each of Ultrawet DS and Monamid 150ADY) was repeated except that after the ore had been ground for 30 minutes with 6.0 lbs/ton of brand sodium silicate the pulp was transferred to the flotation cell and 0.6 lb./ton alum was added as a 1% solution. The pulp was then conditioned for 5 minutes. An exceptionally bright cleaner concentrate (83.2% brightness) was obtained. After fluid energy grinding, brightness was 90.4%. Acid insoluble content of the cleaner concentrate was 97.14%. A comparison of these results with the results of Test No. 2 indicates that the flotation with the combination of reagents was somewhat more selective when alum was present although recovery was reduced.

I claim:

1. In a process for concentrating talc from gangue minerals by froth flotation, the step of frothing an aqueous alkaline deflocculated pulp containing talc and alkaline earth carbonate gangue minerals with a small amount of a nonionic condensation product of diethanolamine and a higher unsaturated fatty acid containing 15 to 21 carbon atoms.

2. The process of claim 1 wherein said fatty acid is derived from soybean oil.

3. The method of claim 1 wherein said pulp contains a dispersant selected from the group consisting of watersoluble alkali metal silicate, alkali metal salt of a condensed phosphate and mixtures thereof.

4. The method of claim 1 wherein said condensation product is the sole frothing agent in said pulp.

5. The method of claim 1 wherein said condensation product is employed in combination with another frothing agent.

6. The method of claim 1 wherein said condensation product is employed in combination with an alkylarylsulfonate frothing agent.

7. The method of claim 1 wherein said condensate product is employed in combination with pine oil frothing agent.

8. The method of claim 1 wherein said pulp has a pH of 9 to 11.

9. The method of claim 1 wherein said aqueous pulp is obtained by wet-grinding talc ore containing carbonate gangue in the presence of an alkaline deflocculating agent and diluting the ground pulp.

10. A method for concentrating talc from finely ground talc ore containing alkaline earth carbonate gangue which comprises dispersing said ore in Water in the presence of a deflocculating agent selected from the group consisting of alkali metal silicate, alkali metal salt of condensed phosphate, and mixtures thereof, conditioning the resulting defiocculated ore pulp for a selective flotation of tale with a small amount of a water-dispersible fatty acid alkanolamide as a frother-promotor, said alkanolamide being the condensation product of 1 mol diethanolamine and 1 mol fatt acid derived from soybean oil, subjecting said pulp to froth flotation at a pH within the range of 9 to 11, and recovering a froth prod uct which is a concentrate of talc.

11. The method of claim 10 wherein said talc ore is wet-ground in the presence of said deflocculating agent before being conditioned for froth flotation.

12. The method of claim 10 wherein a small amount of a soluble aluminum salt is added to the pulp before addition of frothing agent.

References Cited UNITED STATES PATENTS 2,173,909 9/1939 Kritchevsky 209-166 2,442,455 6/194 8 Booth 209166 3,102,856 9/1963 Chase 209166 3,337,048 8/1967 Mencade 2095 OTHER REFERENCES Book Co., Inc.,

HARRY B. THORNTON, Primary Examiner ROBERT HALPER, Assistant Examiner US. Cl. X.R. 209166 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,459,299 August 5 19 Venancio Mercade It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 45, "Walter Eugen Chase" should read Walter Eugene Chase Column 4, line 62 -Sodium silicate solution" should read 0 -Sodium silicate solution Signed and sealed this 28th day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

